When a your guild leader elects to start the event, he will warp them to a special map. When he does this, he'll lose allegiance to your guild and no one else may enter the map until he is brought another Hoe.

In this special map, an NPC, Pierrot Doll will ask you to play a game with her. She will drop 900 Glittering Papers. One of them is special, you'll have to find the right one before 1 minute passes and give it to her. There is no way to tell if you have the special paper other than the fact that it shouldn't stack with the other papers.